My baby now turned 3 months and 5 days old. On his 2 months old, he got cough with phelgm and a bit fever. I brought him to my paed and given some medicine and been asked to switch to soy base milk as well..

Now as he turned to 3 motnhs old, he still with the soy base milk (Nursoy from wyeth). But, I intend to switch back to cow's formula milk. Before Nursoy, I used S26 Gold..And now I wanted to switch back to S26..Should I switch S26 directly or alternately?